NTR-mediated ablation of PCs in adult fish suppresses active avoidance conditioning. A–L, Ablation of PCs. Adult Tg(aldoca:NTR-TagRFPT) fish were treated with MTZ for 18 h (A–F) or left untreated (G–L). The fish were subjected to behavior assays and subsequent histologic analysis 11 d after MTZ treatment. Sagittal sections were stained with anti-Pvalb7 antibody (green). Expression of NTR-TagRFPT (TagRFP, magenta) is also shown. D–F, J–L, High-magnification views of the boxes in A, G. Arrows and arrow heads indicate Pvalb7-positive dendrites of PCs (in the cerebellum) and Type I neurons (in the optic tectum), respectively. The dotted line in G indicates the limit of the cerebellum. Note that the Pvalb7 signal in PCs but not in Type I neurons disappeared and no ML was observed in the MTZ-treated fish. M, N, Turning frequency (turns/min) and swimming speed (mm/s) of Tg(aldoca:NTR-TagRFPT) (aldoca:NTR) and control fish during free swimming (aldoca:NTR; n = 13, control; n = 43). The graph shows the averages and SEs of the data (ns indicates non-significance, *p < 0.05, Welch’s t test). O, Response to electric shocks in adult aldoca:NTR fish treated with MTZ (n = 7). Swimming speed was calculated for 2 s before and after the electric shocks (***p < 0.001, Welch’s t test). P, Swimming speed for 2 s after US in each strain. The graph shows the averages and SEs of the data (ns indicates non-significance, one-way repeated measures ANOVA with Tukey’s post hoc test). Q, Percentage of active avoidance learners of aldoca:NTR (n = 13) and control wild-type (n = 43) fish (**p < 0.01, Fisher’s exact test). Va, valvula cerebelli. The other abbreviations are described in Figure 1. Scale bars: 400 μm (A; applies to A–C, G–I) and 200 μm (D; applies to D–F, J–L). ns, not significant.
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